Power-Law Nanofluid Magnetohydrodynamics Combined Convection in the Presence of Heat Absorption/Generation: A Lattice Boltzmann Analysis to Compute Thermal Performance Index

Abstract

Endeavors to improve the performance of thermal systems have always been of great noticed due to their extremely high importance in industrial and engineering applications. For this intention, in the existing simulation, several effective strategies have been evaluated to determine the amount of heat transfer and entropy formation caused by the combined convection of non-Newtonian nanofluid with particles Brownian motion. Based on the findings via LBM simulation, it has been observed that changing the position and speed direction on the chamber wall helps to control the flow characteristics, and thus significantly changes the thermal performance of the system. The least effect of the magnetic field in reducing the value of the Nusselt number in all the positions of applying the speed belongs to the state where the wall direction is aligned with the force of gravity. In the case where the middle part of the vertical wall has speed, the formed flow power inside the chamber is 29% and 45% higher than when the first third and the last third of the wall have speed. The presence of a strong magnetic field leads to the reduction of convection effects, which is more evident for moving up the vertical wall. When the middle part of the wall has speed, if the magnetic field is applied to the middle part of the chamber to the highest value, the reduction of the average Nusselt number is about 35% and 39% more than the case when the magnetic field is applied to the first third and the last third of chamber. To have a higher average Nusselt number value, reducing the fluid power-law index and enhancing the Reynolds number value are effective strategies. To control the effects of the magnetic field, it is very effective to reduce the shear force on the chamber wall and expose the fluid flow to the heat absorption/production phenomenon. By reducing the value of fluid power-law index, the effect of magnetic field and heat absorption/production becomes more evident. In Re=200, the reduction of the thermal performance index for enhancing the Hartmann number value to the highest value is about 39% for n = 0.45, while this effect is about 31% and 24% for n = 0.7 and n = 0.95, respectively. By exposing the current to heat production, the effect of the magnetic field is reported to be about 55% higher than in other cases. Although heat production enhances the amount of Be value by about 66% compared to the heat absorption mode, it leads to an increase in the thermal performance index. The highest value of the system thermal performance index (0.82) can be achieved by upward moving the middle part of the chamber wall in the absence of magnetic field for heat absorption mode at the lowest power-law index and the highest Reynolds number value.